"One lady was crying," Adjodha told Newsweek. "She was saying that we shouldn't have played the trailer. That this was wrong."

Universal Studios in Los Angeles said it had no plans to pull the trailer for the film, which is scheduled to open in theaters on April 28.

"Because `United 93' deals with the most emotional, tragic day in recent American history, we expect that some moviegoers will have a strong response to its images and narrative," the studio said in a statement. It said its marketing materials should retain the movie's realism, "so that those who elect to see the film will be prepared for the experience."

"United 93" is scheduled to make its world premiere on the Tribeca Film Festival's opening night. The festival, which was created to help lower Manhattan recover economically from the 2001 attack, begins April 25 and runs through May 7.

"We are very supportive of the film," said festival publicist Tammie Rosen.

The trailer begins with images of passengers boarding the plane on a sunny morning, and builds to a disturbing scene that includes news video of a plane about to hit the World Trade Center. It then returns inside Flight 93 as terrorists begin the hijacking.

Director Paul Greengrass, whose past films include "Bloody Sunday," a dramatization of a 1972 massacre in Northern Ireland, consulted with the families of Flight 93 victims while making the film.

Families of Flight 93, a nonprofit group that represents some relatives, has praised the movie, and Universal Pictures has pledged to donate 10 percent of the first three days of the film's grosses to the Flight 93 National Memorial.

The trailer, though, caught some viewers by surprise in New York, where it was being shown before "Inside Man," a Spike Lee thriller.

Georgia Levis, a research scientist who lives in Manhattan, said she watched with a lump in her throat.

"As a New Yorker, I had very mixed feelings: Part curiosity, part disgust because I hate to reopen that wound," she said after leaving a theater. "It was very emotional. I felt like I wanted to cry."

She wondered whether she would "have the guts" to see the movie.

Erin Johnson, who works at one of the Manhattan theaters showing the trailer, said it may be too soon for some.

"To me, it brought back bad memories," she said. "Picturing yourself where you were when it happened, picturing the smoke."

The plane crashed in a field near Shanksville, Pa., as passengers tried to take control of the cockpit. The plane was en route from Newark, N.J. to San Francisco.

A made-for-TV film about the hijacking, "Flight 93," drew 5.9 million viewers when it aired on A&E in January, making it the network's most-watched program ever. The Discovery Channel also re-enacted the events in the documentary "The Flight That Fought Back."

The trailer is being shown on about 3,000 screens across the United States.

In place of the trailer, some movie theaters are showing a promotional spot about the making of "United 93," explaining the thinking and methodology behind it.